(declare-fun a () String)
(declare-fun b () String)
(assert (str.in.re (str.++ a "z" b) (re.* (str.to.re "b"))))
(assert (str.in.re (str.++ a "z" b) (re.+ (re.+ (str.to.re "b")))))
(assert (str.in.re (str.++ a "z" b) (re.* (str.to.re "zaa"))))
(assert (str.in.re (str.++ a "z" b) (re.opt (str.to.re "z"))))
(assert (str.in.re a (re.opt (re.range "a" "u"))))
(check-sat)
